The Földes–Hammer Characterization of Split Graphs

Arthur Freitas Ramos 📧, David Barros Hulak and Ruy Jose Guerra Barretto de Queiroz

September 11, 2026

Abstract

This entry formalizes the classical Földes–Hammer theorem characterizing finite split graphs as exactly the graphs with no induced copy of \(2K_2\), \(C_4\), or \(C_5\). It builds on the AFP session Undirected_Graph_Theory.

License

BSD License

Note

Codex with gpt 5.5 on xhigh reasoning was used to help with proof engineering.

Topics

Session Foldes_Hammer

Depends on

Cite

× 
@article{Foldes_Hammer-AFP,
  author  = {Arthur Freitas Ramos and David Barros Hulak and Ruy Jose Guerra Barretto de Queiroz},
  title   = {The Földes–Hammer Characterization of Split Graphs},
  journal = {Archive of Formal Proofs},
  month   = {September},
  year    = {2026},
  note    = {\url{https://isa-afp.org/entries/Foldes_Hammer.html},
             Formal proof development},
  ISSN    = {2150-914x},
}
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